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5.1. INTRODUCTION TO SOIL SYSTEMS (Knowledge and understanding (soil…
5.1. INTRODUCTION TO SOIL SYSTEMS
Knowledge and understanding
soil system is a dynamic ecosystem that has inputs, outputs, storages and flows
the quality of soil influences primary productivity of an area
the soil system may be illustrated by a soil profile - layered structure (horizons)
soil system storage includes organic matter, organisms, nutrients, minerals, air and water
transfers of material within the soil include biological mixing, leaching (minerals dissolved in water moved through soil) - contributes to organisation of soil
inputs - organic material including leaf litter and inorganic matter from parent material, precipitation and energy
outputs - uptake by plants and soil erosion
transformations - decomposition, weathering and nutrient cycling
What is soil?
complex ecosystem made up of minerals, organic material, gases, and liquids
What is it made from?
mineral particles mainly from underlying rock
organic remains that come from plants or animals
water within spaces between soil grains
air within soil grains
typically has 50:50 ratio between mix of solids and pore spaces - pore spaces contain variable amounts of water and air
Horizons
In a cross section, soils have a profile which is modified over time - organic material leaches downwards, mineral materials move up - these processes sort the soil into visible horizons
Porosity, permeability and pH
Porosity - amount of space between particles
Permeability - ease at which gases and liquids can pass through the soil
Acidification of soil - major impacts on forestry in N Europe where acid rain has made soil more acidic
Soil sustainability
Fertile soil is a non renewable resource - can not be replaced quickly
fertile soil has enough nutrients for healthy plant growth - main nutrients are nitrates, phosphates and potassium (NPK) and also many micronutrients - these can be leached out of the soil or removed when a crop is harvested so they have to be replaced in agriculture by chemical fertiliser, growing legumes, crop rotation or through application of organic matter e.g. manure or compost